(1) Field of Invention
The present invention relates to the field of computer-aided design apparatus, and more particularly, to apparatus for the design of three-dimensional objects to be fabricated. The invention is particularly applicable to the design of complex objects made up of over 5,000 constituent parts.
(2) Discussion of Related Art
There are many examples of fabricated objects, such as urban agglomerations, buildings and building complexes, industrial plants and power generating plants, transport terminals, oil rigs, aeroplanes, cars, trucks and trains, ships, satellites and spaceships, micro-chips, nanotechnology structures, etc.
These objects are fabricated by assembling together small units that in turn become parts to larger components. Fitting them together involves complex interrelations of a great amount of individual shapes. Furthermore, the fitting together of components involves complex physical interactions which are dependent not only on the components themselves, but also the topology of the overall structure and the relative positions which the components occupy within this topology.
Existing computer-aided design systems for fabricated objects require the user to create constituent components of the design in design files which for historical reasons emulate the traditional design techniques that served the bottom-up approach to building construction.
Components from the design file are then exported into an overall space for the model, where each component is manually placed into position so that the components fit together and generate the topology of the overall model.
Accordingly, the design, placement and fitting of components are separate tasks in existing systems.
By way of example, “Interactive Design of 3D Models With Geometric Constraints” by van Emmerik MJGM in The Visual Computer, Springer-Verlag, volume 7, 1991, pages 309-325, XP009088118, presents an interactive graphical approach for the design of parameterized part-hierarchies. Primitive solids can be grouped into compound objects, and multiple instances of a compound object can be used in further designs. Geometric relations between primitives and instances are specified by geometric constraints between their local coordinate systems.
These systems suffer from a number of problems, however.
In particular, considerable effort and time is required on the part of the user to create the design in an existing system. This defeats the purpose of computer support. For example, variations in the components can only be introduced by redesigning components in the design files and then placing them manually to recreate the overall model. Also, the consistency of such designs relies upon the designer's ability to check for and iron out inconsistencies (such as objects which encroach upon each other—that is, they occupy the same space). How real this problem is shown by the fact that most existing systems provide so called ‘interference checking’ devices to check for inconsistencies such as encroaching objects.
Such systems have therefore forced designers to create regular-shaped fabricated objects, using repeatable design patterns and compositions of copies of the same components, to the detriment of functionality, all while the demand for increasingly articulate and diversified large fabricated objects grows rapidly. In fact so great is the problem, that any small improvement in the design process which reduces the problem is hailed as a breakthrough.
A further problem is that a building component manufactured according to a design from a system which designs, places and fits the components as separate tasks is often not consistent with the huge amount of other components that are to form the fabricated object. As a result, skill-intensive labour is required to fit the components together.
Experience of using components manufactured from a design created by existing systems has given rise to the commonly held belief that it is sometimes quicker and cheaper to fine tune the fittings of components on site (or return them to the factory for adjustment) than to spend the time that is required by existing design systems to design components that will fit without adjustment. Waywardly, the responsibility for fitting of components is thus passed from the designer to the builder. This particular problem in the design and construction of buildings defeats the fundamental purpose of design which is that it should be complete and consistent before the fabrication stage. With the growing relevance of information technology, completeness and consistency become requirements in rigorous (logical) terms. This makes the problem even more acute.
For the same reasons, the synergy of industrial production of components, relying on numerically controlled machines and robots in production lines is hugely underemployed in building construction. The cost of building components is out of step with the cost of other industrial products that are no different in terms of materials used or energy consumed in their production.